Stent grafts are used to replace or repair vessels of the body such as the blood vessels. A stent graft is usually formed from a tubular body of a biocompatible graft material and one or more stents are mounted into or onto the tubular body to provide support for the tubular body. The stents may be balloon expandable stents or self-expanding stents. This invention will be discussed with reference to the use of self-expanding stents but the invention is not limited to that and may be used with balloon expandable stents or other forms of stents.
Where a stent graft is to be placed into a curved blood vessel, and it is desired to maintain that curve, it is desirable to have the stent graft set into the approximate shape of the curve to prevent buckling of the stent graft in the vessel which may occlude some of the flow path in the vessel.
Stent grafts are deployed using endovascular techniques on an introduction device in which the stent graft is retained in a radially contracted condition by a sheath. Upon retraction of the sheath and release of any retention arrangement where necessary, where the stent graft has self expanding stents, the stent graft can expand under the action of the self expanding stents towards the vessel walls to define a blood flow path and the introduction device can be withdrawn.
There can be a problem with mounting of a stent graft designed for a curved vessel onto an essentially straight catheter of a deployment device. The catheter of a deployment device is essentially straight to enable it to be introduced through the vasculature of a patient via a femoral artery using the Seldinger technique.
It is an object of this invention to provide a stent, stent graft incorporating the stent which stent graft will form at least in part the shape of a curved vessel and to a method of deploying such a stent graft or to at least provide the physician with a useful alternative.
Throughout this specification the term distal with respect to a portion of the aorta, a deployment device or a prosthesis means the end of the aorta, deployment device or prosthesis further away in the direction of blood flow away from the heart and the term proximal means the portion of the aorta, deployment device or end of the prosthesis nearer to the heart. When applied to other vessels similar terms such as caudal and cranial should be understood.
The term normal in relation to a stent is used to describe a stent which comprises a wire formed into a plurality of struts and bends between adjacent struts, the struts defining a cylindrical body and the bends at each end defining respective planes transverse to the longitudinal axis of the cylindrical body with the planes substantially parallel to each other and substantially at right angles to the longitudinal axis of the cylindrical body.